1. Field of the Invention
The present invention relates to a technology for embedding information into image information.
2. Description of the Related Art
Following operations are generally carried out in an image processing application.
1. Encoding of an image
2. Recording and storing of specific information of the code
Generally, the specific information in the operation above is handled as management information based on the operation above, as much as possible. For example, according to the International Standard (IS) 15444-1(Joint Photographic Experts Group (JPEG) 2000 Part1), an image encoding system concerning the above 1 is prescribed by the following eight items, and these items correspond to Annex A to Annex H, respectively.
a. Code stream syntax
b. Order of image and compressed image data
c. Arithmetic entropy encoding
d. Coefficient bit modeling
e. Quantization
f. Discrete wavelet transform of a tile component
g. Direct current (DC) level shift and plural component transform
h. Encoding of an image having an area of interest
On the other hand, the above 2 is prescribed by the Annex I as follows.
i. JP2 file format
One example of specific information included in the above i is a display area of an image. A vertical size and a horizontal size of a display area are prescribed by pixels using HEIGHT and WIDTH of elements defined as Image Header box in I.5.3.1.
Other box information is also used to record and store specific information of a code. A further detailed explanation is prescribed in the IS15444-1(JPEG2000 Part1) Annex I.
Techniques for embedding certain information into information such as an image to be encoded are conventionally known. See, for example, Japanese Patent Application Laid-Open No. H10-84484. The following three methods of embedding information are generally known.
A first method of embedding information is to embed information into an area that a user and each manufacturer can freely use in an optional marker segment, or a file format box or a field. When encoding and decoding are to be carried out among different manufacturers following the international standard, it is necessary to check data compatibility before and after the encoding and decoding in order to determine whether the encoding and decoding operations are consistent with the international standard specifications.
A marker segment prescribed by the international standard includes an essential marker segment that becomes a basis of determining whether the encoding and decoding are consistent with the international standard specification, and an optional marker segment into which each vendor can freely set information.
A com marker for comment is an example of an optional marker segment prescribed by the IS15444-1 (JPEG2000 Part1). A universal unique identifier (UUID) is available as a file format box.
These areas are not necessarily compatible. However, each vendor and each user can freely use these areas. For example, these areas are often used as areas for indicating a copyright notice of an image.
A second method of embedding information is to embed an electronic watermark into an image. When the image embedded with the electronic watermark is to be encoded, it is possible to effectively detect a tampering of a part of the image or a tampered position.
A third method of embedding information is to embed information using a mechanism of managing embed information separately from the image, and to access the embedded information through a route independent of that of the image information. Many vendors effectively use this method when there is no mechanism of embedding information in an encoding stream or when a server and a client can secure a route for exchanging information independent of the image.
However, the above three systems have many problems. In the first method, the embedded marker segment and the embedded file format box are not essential areas. When a particular manufacturer embeds information into an image at an encoding time, and then the image is expanded using an expander manufactured by a different manufacturer, edited, and compressed again, there is no guarantee that the optional marker segment and the optional box are stored.
Therefore, even when the code is expanded using an expander manufactured by the first manufacturer, the specific information embedded into the document at the beginning may be deleted, and the embed information may not be stored successfully in some cases.
The algorithm of the electronic watermark in the second method is not standardized between countries. Therefore, the algorithm is not compatible. Even when the embedded information is small, since the same information is redundantly embedded into the whole image at various positions to detect a tampering and a tampered position, the file needs to have a large size despite the small amount of embedded information.
In the third method, a mechanism of handling the embed information and the image information in a pair is essential. Therefore, the embedded information cannot be properly accessed with an expander that does not have this mechanism.